The present invention relates to a method for rejecting a filter bag for infusion products and the device that implements said method and that forms part of a machine producing filter bags.
Machines producing filter bags generally comprise a plurality of work stations, installed in sequence along the respective production lines where the filter bags are completed, each containing a charge of the product sealed in a corresponding section or chamber in the filter bag. Either single or double-chamber filter bags can be used, depending on the type of product and machine model; a connecting string is attached to the filter bag, adopting a number of alternative known methods (by knotting, heat sealing or by means of a heat sealed stamp, for example) and a pick-up tag is attached to the free end of the string, using a number of alternative known methods (by knotting, heat sealing or by means of a heat sealed stamp, for example).
The string and pick-up tag are positioned on the filter bag (for example, by winding the string around the bag and attaching it to or tucking it inside the bag) to complete a product ready for grouping and stacking in a filter bag stacking station, followed by a final packaging step, comprising the packaging of the filter bag stacks or groups of stacks in cartons or boxes.
Before moving on to the stacking step described above, each filter bag is generally individually wrapped, using a sheet of overwrapping paper suitably folded into a U shape over itself to enclose the filter bag and sealed in one of two different ways: along at least two longitudinal sides or edges of the overwrapping paper sheet if the sheet has an opening flap folded over onto its surface; or sealed simultaneously along three edges of the sheet, namely two longitudinal edges and the upper transversal edge, if a simplified type of overwrapping without flap is being made.
At present, the manufacturing of each filter bag and the application of the string and tag is controlled and checked along the path followed by the filter bag by sensors installed in the above-mentioned work stations.
These sensors are designed to detect the presence of any defects or faults in the filter bags, for example, if the bag is not properly sealed, and/or has not been filled with an adequate quantity of the infusion product, and/or the pick-up tag and/or connecting string have not been attached or have been attached incorrectly, etc. The sensors then send an error signal to the control unit installed in the manufacturing machine.
When a rejection signal is given by the control unit in the manufacturing machines currently in use, a bag cannot be rejected until the step of packing the filter bag stacks in boxes has been completed.
In other words, when a single defective filter bag is detected, the entire box or carton containing one or more stacks of filter bags has to be rejected. Moreover, in many cases, this operation has to be carried out by hand.
Up to now, it has not been possible to modify the structure of the manufacturing machine in such a way that bags can be rejected automatically prior to the packaging step, without greatly increasing the structural complexity of the machine as a whole.
The aim of the present invention is therefore to eliminate the above mentioned problem through a method for rejecting an individual defective filter bag, and the related device implementing the method, prior to the above-mentioned packaging step, without altering the traditional structure of the manufacturing machine.
Accordingly, the present invention provides a method for rejecting a filter bag for infusion products in a manufacturing machine, said method comprising a step of feeding the filter bag along a production line to a plurality of work stations, installed in sequence along the line, where the filter bag is completed by attaching a connecting string and pick-up tag; a step of detecting and inspecting the filter bag as it is being completed; and a step of feeding the filter bag towards an intermediate station where it is picked up and transferred to a subsequent stacking station for the forming of stacks of a preset plurality of filter bags. The method is characterised in that it comprises a step of disabling the feed motion of the defective filter bag towards the pick-up station when a defect or fault is detected in the filter bag, and a step of rejecting and expelling the defective filter bag.
The present invention also provides a device for rejecting filter bags for infusion products installed in manufacturing machines, the filter bags comprising at least one chamber containing a charge of the product and a string joining at least one chamber to a pick-up tag, each attached to one end of the string; the device comprising handling means for moving the filter bags along a production line where at least the following are installed in sequence: a station for attaching the string to the filter bag; a station for attaching the pick-up tag to the string and positioning the string and pick-up tag on the filter bag; an intermediate station for picking up the completed filter bag and transferring it to a stacking station where stacks are formed with a set number of filter bags; sensors installed at least in the string and pick-up tag attachment stations for detecting and inspecting the filter bag and sending an error signal to the control unit if the filter bag is defective. The device is characterised in that it also comprises means for disabling the feeding of the defective filter bag, installed and operating in the proximity of the handling means and designed to prevent the defective filter bag from being transferred from the handling means to the intermediate pick-up station; and means for expelling the defective filter bag from the handling means.